Dental cavities may protect against oral, throat cancers

(CBSNews.com) - Cavities may not make your dentist too happy, but cancer doctors on the other hand may feel differently following new research.

A study finds people with more dental cavities are significantly less likely to be diagnosed with head and neck squamous cell carcinoma.

The cancers start in the squamous cells of our bodies, which line the moist, mucus membrane surfaces inside the head and neck like the mouth, back of the throat (oropharyngeal), nose and larynx (vocal cords).

This year about 50,000 Americans will be diagnosed with head and neck cancer. About 90 percent of head and neck cancers are considered squamous cell carcinomas,Ohio State Universitynotes.

That's where cavities can come in. Cavities, or dental caries, are the second-most common health condition, only behind the common cold, theNational Institute of Healthnotes. Bacteria normally found in the mouth that help digest foods combine with food pieces, acids and saliva to form plaque. Plaque builds up to form tartar, which can irritate the gums and cause inflammation, resulting in gingivitis and periodontitis.

The longer plaque sticks, it turns into lactic acid, which is caused by the breakdown of carbohydrates by mouth bacteria. This damages the enamel coating of on our teeth, causing holes from tooth decay.

However, earlier research suggests these bacteria may elicit an immune system response, a so-called "Th1 cell response," that has been consistently linked to lower cancer risk. The bacteria behind gum disease, on the other hand, have been linked to increased cancer risk.

Researchers from the University of Buffalo in New York decided to put these theories to the test. They recruited 399 people who were diagnosed with head and neck squamous cell carcinoma between 1999 and 2007, and compared them to 221 control subjects who hadn't been diagnosed with any cancer.

Subjects were split into three groups, from least cavities to most. Those in the upper-third cavity group were less likely to have these cancers of the mouth or oropharynx than those in the lower-third. There was no difference seen for laryngeal cancers.

The researchers said the lactic acid bacteria that causes cavities may in fact protect these mucosal surfaces in the head. The researchers suggest cavities may not be all that bad considering these possible protective benefits.

"We could think of dental caries as a form of collateral damage and develop strategies to reduce its risk while preserving the beneficial effects of the lactic acid bacteria," they concluded.

They called their findings "unexpected" because cavities are a sign of poor oral health, and poor oral health has been linked to an increased risk of cancer.

Possibly better ways to reduce oral cancer risk though are not drinking or smoking, which are both risk factors. There were significantly more smokers and drinkers in the cancer group compared to the control subjects.

One expert disputed the study, noting it had many limitations, including a small sample size and the fact it only looked at current cavities instead of lifetime history.

"The authors and correlation do not prove cause and effect," Dr. Joel Epstein, a diplomat of the American Board of Oral Medicine, toldHealthDay. "Also, even if caries is associated with reduced cancer risk -- seems very unlikely -- the dental damage, and infection risk of dental disease carries its own risk."

Poor oral health in general is considered a major U.S. problem, given many Americans can't afford necessary care.